The one-sided overhand bend is a knot used in rock climbing and mountaineering as a rappel knot. It is also known as the binder's knot and the overhand knot.

An "Offset Overhand Bend" (OOB) is a simple method of joining two cords or threads together. This knot is used (with long tails) in rock climbing for joining two ropes for a rappel. American climbers often refer to it as the European Death Knot. Though it is not so strong, it is easy to tie, and since it is "offset" it slides over edges more easily than other knots, easing rope retrieval; its small size also reduces its chance of getting stuck. It can be made more secure by tying off one end around the other with an overhand stopper knot, snug to the OOB body. If the ropes are of different diameters (or flexibility), the thinner (or more flexible) rope should be in the position shown in the image by the blue rope, and the safety overhand stopper should be tied with this.

A similar knot, the "Offset Figure of Eight Bend" has been used in the belief that its greater size brings more security but the evidence of at least one tragic failure and some testing shows the knot to be if anything less secure, more prone to capsize and in doing so to consume much more of the ends than does an OOB. Moreover, while there is one obvious proper dressing of the OOB, there are a couple of dressings that can arise for the offset figure of eight.

Outside of rockclimbing, the OOB is fairly commonplace, as it is a quite simple and easily tied bend. It is used, for example on shopping tag strings. The knot has also been called "Flat Overhand", "Double Overhand", and "Thumb Bend"; the first name is a misnomer, the second has an other, established denotation, and the third while good doesn't provide for the subclass of these offset bends.